The growing importance of alternative energy sources has brought a renewed interest in the Fischer-Tropsch synthesis as one of the more attractive direct and environmentally acceptable paths to high quality transportation fuels. The Fischer-Tropsch synthesis involves the production of hydrocarbons by the catalyzed reaction of CO and hydrogen. Commercial plants have operated in Germany, South Africa and other parts of the world based on the use of particular catalysts. The German commercial operation, for example, concentrated on the use of a precipitated cobalt-thoria-kieselguhr fixed-bed catalyst, and a later modification where MgO, for economy reasons, replaced part of the thoria.
More recently, U.S. Pat. No. 4,088,671 to T. P. Kobylinski describes the use of a ruthenium-promoted cobalt catalyst on a support, such as alumina or kieselguhr, in the synthesis of hydrocarbons from the reaction of CO and hydrogen at substantially atmospheric pressure. The patent discloses that the molar ratio of cobalt to ruthenium in the finished catalyst can suitably be from 5:1 to about 200:1, is more usually 10:1 to 100:1, and most usually it is from 15:1 to 80:1. As ruthenium is expensive, the patent indicates that it is preferred to employ ruthenium in the minimum amount necessary to achieve the desired result (column 2, lines 60-67). The minimum amount of ruthenium disclosed in relation to cobalt is a molar ratio of cobalt to ruthenium of 200:1 (column 2, line 62). Further, the patent indicates that the method employed to deposit the catalytic materials is not critical, but discloses the use of aqueous solutions of metal salts to prepare the catalyst (column 3, lines 27-38).